Abstract: A system for compensating for phase noise, with particular application in lidar, includes a compensation interferometer that receives a signal from a source, and splits it into a first and second path, with a path length difference ?? between them. Typically the path length is significantly less than that of the return distance to a target. The output of the compensation interferometer, which consists of phase noise generated in time ?? is vectorially summed during a time similar to a signal flight time to a target, and the result used to reduce phase noise present on measurements of a target. It further includes means for selecting ?? such that competing noise elements are reduced or optimised.

Abstract: A system for compensating for phase noise, with particular application in lidar, includes a compensation interferometer that receives a signal from a source, and splits it into a first and second path, with a path length difference ?? between them. Typically the path length is significantly less than that of the return distance to a target. The output of the compensation interferometer, which consists of phase noise generated in time ?? is vectorially summed during a time similar to a signal flight time to a target, and the result used to reduce phase noise present on measurements of a target. It further includes means for selecting ?? such that competing noise elements are reduced or optimised.

Abstract: Some embodiments are directed to a multiplexed fiber sensor for a fiber optic hydrophone array, including a signal receiver configured to receive a signal from the fiber optic hydrophone sensor array and an interferometer. The interferometer is configured to produce a first signal component and a second signal component from the signal received from the hydrophone array, and also provided with a first polarization controller configured to control the polarization of the first signal component and a second polarization controller configured to control the polarization of the second signal component. A modulated carrier signal generator configured to generate a modulated carrier signal component based on the first signal component is also provided. A detector configured to output a demodulated output signal from the modulated signal component and the second signal component is included, wherein the modulated signal component and the second signal component output separately from the interferometer.

Abstract: Some embodiments are directed to a multiplexed fiber sensor for a fiber optic hydrophone array, including a signal receiver configured to receive a signal from the fiber optic hydrophone sensor array and an interferometer. The interferometer is configured to produce a first signal component and a second signal component from the signal received from the hydrophone array, and also provided with a first polarisation controller configured to control the polarisation of the first signal component and a second polarisation controller configured to control the polarisation of the second signal component. A modulated carrier signal generator configured to generate a modulated carrier signal component based on the first signal component is also provided. A detector configured to output a demodulated output signal from the modulated signal component and the second signal component is included, wherein the modulated signal component and the second signal component output separately from the interferometer.

Abstract: Apparatus (100) is provided which is arranged to accept an input data stream. In some embodiments, the apparatus (100) comprises a sampler arranged to sample the input data stream to provide k samples thereof, wherein each of the samples is n bits long and a string selector arranged to select m binary strings n bits long from at least a chosen subset of all random binary strings of a predetermined length. The apparatus (100) may further comprise a logical operator arranged to perform a logical function for each of the k samples with each of the selected binary strings to provide a vector, a memory arranged to store a matrix of the vectors generated from k samples, and an address generator arranged to generate RAM address segments from the matrix. In embodiments, the apparatus (100) may comprise a processor for, for example, pattern matching; feature detection, image recognition.

Abstract: Range-finding apparatus comprises a source of pulsed radiation of variable repetition rate and a beam-splitter for dividing the pulsed radiation into two portions which are directed respectively to a local retro-reflector and to a retro-reflector co-located with a remote target the range of which is to be determined. The source, beam-splitter and retro-reflectors are arranged in the form of Michelson interferometer together with a detector. The repetition rate of the source is tuned to frequencies f such that round-trip distance to the remote target is mc/f where m is an integer, this condition being detected by observing a heterodyne signal at the detector. Two such frequencies enable range to be determined. The precision with which range is determined may be increased by carrying out interferometry using the two portions. The accuracy of the method does not depend on absolute range (as with triangulation) and is not limited by the speed of timing electronics, as is the case for time-of-flight techniques.

Abstract: Apparatus (100) is provided which is arranged to accept an input data stream. In some embodiments, the apparatus (100) comprises a sampler arranged to sample the input data stream to provide k samples thereof, wherein each of the samples is n bits long and a string selector arranged to select m binary strings n bits long from at least a chosen subset of all random binary strings of a predetermined length. The apparatus (100) may further comprise a logical operator arranged to perform a logical function for each of the k samples with each of the selected binary strings to provide a vector, a memory arranged to store a matrix of the vectors generated from k samples, and an address generator arranged to generate RAM address segments from the matrix. In embodiments, the apparatus (100) may comprise a processor for, for example, pattern matching; feature detection, image recognition.

Abstract: A structured light generator for illuminating a scene comprising a light source and a light guide comprising a tube having a longitudinal axis and having substantially reflective sides arranged to project an array of distinct images of the light source towards the scene in the manner of a kaleidoscope, wherein including a light deflection element to redirect light so that the projection axis and the light guide axis are angled with respect to one another. In this way the light guide, which is typically an elongate structure, can be ‘folded’ away from the direction of light projection, which offers advantages in terms of packaging of the light generator where thickness in the direction of projection is desirably minimised.

Abstract: An optical correlation apparatus is described which forms first and second parallel optical signals in response to a serial input data stream. The first parallel optical signal is arranged to have bright pulses represent binary 1 and the second parallel optical signal is arranged to have bright pulses represent binary 0. A channel select means, such as an optical switch or amplitude modulator, deselects or blocks channels in the first parallel optical signal which correspond to binary 1 in a reference data string and also deselects or blocks channels in the second parallel optical signal which correspond to binary 0 in the reference data string. The remaining optical signals are combined at one or more detectors. Where the input data matches the reference data string each bright pulse in the first and second parallel optical signals is deselected and the detector registers zero intensity. However when there is any mismatch at least one channel will pass a bright pulse to the detector.

Abstract: The invention provides a mould (80) comprising first (82), second (84) and third (86) cuboid moulds elements, each having a pair of adjacent rectangular faces which are planar and polished flat and which intersect at 270° to a high tolerance. Each mould element has a length dimension substantially twice its width dimension so that the mould elements may be arranged to form two accurate internal corner-cubes having flat, planar surfaces suitable for moulding. The apexes of the two internal corner-cubes are co-located. Pairs of adjacent mould elements are clamped in contact with each other by means of bolts (88) and washers (89). The mould may be used to produce a component having a very accurate solid corner-cube, whilst the mould elements themselves are relatively simple to fabricate because each is required to have only a pair of adjacent rectangular surfaces which are flat and planar and which intersect at 270° to a high tolerance.

Abstract: An optical tag (200) comprises a chalcogenide glass corner-cube reflector (202) bonded to a silicon MEMS modulator (206) by means of a glass material (214) having a lower softening temperature than that of the reflector. The tag is provided with AR coatings (210, 212). The invention provides a robust, integrated and compact optical tag having a wide field of view and low manufacturing costs.

Abstract: Range-finding apparatus comprises a source of pulsed radiation of variable repetition rate and a beam-splitter for dividing the pulsed radiation into two portions which are directed respectively to a local retro-reflector and to a retro-reflector co-located with a remote target the range of which is to be determined. The source, beam-splitter and retro-reflectors are arranged in the form of Michelson interferometer together with a detector. The repetition rate of the source is tuned to frequencies f such that round-trip distance to the remote target is mc/f where m is an integer, this condition being detected by observing a heterodyne signal at the detector. Two such frequencies enable range to be determined. The precision with which range is determined may be increased by carrying out interferometry using the two portions. The accuracy of the method does not depend on absolute range (as with triangulation) and is not limited by the speed of timing electronics, as is the case for time-of-flight techniques.

Abstract: An optical correlation apparatus is described which forms first and second parallel optical signals in response to a serial input data stream. The first parallel optical signal is arranged to have bright pulses represent binary 1 and the second parallel optical signal is arranged to have bright pulses represent binary 0. A channel select means, such as an optical switch or amplitude modulators deselects or blocks channels in the first parallel optical signal which correspond to binary 1 in a reference data string and also deselects or blocks channels in the second parallel optical signal which correspond to binary 0 in the reference data string. The remaining optical signals are combined at one or more detectors. Where the input data matches the reference data string each bright pulse in the first and second parallel optical signals is deselected and the detector registers zero intensity. However when there is any mismatch at least one channel will pass a bright pulse to the detector.

Abstract: This invention relates to a ranging apparatus capable of ranging simultaneously to a three dimensional scene. An illumination means (22) illuminates a scene with a two dimensional array of spots (12). A detector (6) is located near to the illumination means (22) and arranged to look toward the scene. A processor (7) responds to the output from the detector (6) and, from the location of a spot in the image of the scene, determines the range to that spot. A variety of techniques are used to resolve ambiguity in determining which projected spot is being considered.

Abstract: An optical substrate is provided with a surface of a desired shape by coating the surface with a thin layer of an optical glass and subsequently modifying the shape of the external surface of the layer. In preferred embodiments, the temperature of the substrate is maintained at substantially less than 400° C., the substrate is an optical component other than a simple window, and the refractive index o the optical glass is within 20% of the refractive index of the material providing the surface to be coated. One particular use is when both the substrate (e.g. a non-linear optical layer) and the optical glass are optically transmissive in the near infra-red and/or mid infra-red ranges. The glass layer can compensate for physical imperfections in the surface. It can be polished to optical quality, or provide with detail across the coated surface, e.g. as a “moth-eye” anti-reflection layer, or a diffractive or interference structure.

Abstract: A resonant power circuit which supplies pulsed power to a load, such as a pulsed laser, from a d.c. supply by cyclically charging a capacitor. The capacitor is discharged through the load on closure of a switch which should then open to allow the capacitor to re-charge. Occasionally the switch fails to open and the circuit of the invention then develops and applies a reverse voltage to the switch to force it to become open circuit.